Method for electrolytic determination of lead and copper



March 13, 1951 2,544,802

R. W. NOTVEST METHOD FOR ELECTROLYTIC DETERMINATION OF LEAD AND COPPER Filed Feb. 10, 1948 Patented Mar. 13, 1951 METHOD FOR ELECTROLYTIC DETERMINA- TION OF LEAD AND COPPER Robert W. N otvest, Affton, Mo., assignor to American Brake Shoe Company, New York, N. Y., a. a corporation of Delaware Application February '10, 1948, Serial No. 7,366

1 Claim.

This application is a continuation-in-part of applicants copending application, Serial No. 549,995, filed August 18, 1944 and entitled Method of Electroanalysis', now abandoned.

This invention relates to a method for the electrolytic quantitative analysis or determination of copper and lead in copper-bearing and lead-bearing metals or alloys.

In the uantitative analytical determination or analysis of copper and lead in copper-bearing and lead-bearing metals or alloys, or other specimens, in acid solutions, these metals are electrolytically deposited as metallic copper and as lead oxide (PbOz) upon a platinum wire gauge cathode and anode, respectively, of known weight. In the case of copper, the copper content of the metal or other specimen under analysis is then determined by calculating the difference in the weight of the platinum cathode before and after the copper is deposited thereon. Similarly, in the case of lead, the lead content of a metal or other specimen under analysis is calculated by determining the Weight of the lead oxide (PbO2) deposited upon the platinum anode and then calculating the weight of the lead in the deposited lead oxide in .accordance with the percentage composition of the lead oxide.

However, a numberof problemshave been experienced heretofore in the electroanalysis of copper and lead in acid solutions and these problems have not heretofore, insofar as I am aware,

been successfully solved.

Thus among the problems which have been experienced heretofore in the quantitative electrolytic determination of copper and lead in copper-bearing and lead-bearing metals or alloys in acid solutions are the fact that such metals or other specimens usually contain small percentages of arsenic, iron, sulphur and phosphorus, and the presence of small percentages of these elements, and resulting deposits thereof upon the platinum electrodes materially complicatesthe problem of making accurate analytical determinations of the cop-per and lead contents of such metals or other specimens. Hence it has been customary practice heretofore in the art to remove these elements, as well as other elements to adhere firmly to the cathode.

including antimony, tin, molybdenum, gold, platiantimony, tin, molybdenum, gold, platinum, silver, mercury, bismuth, selenium and tellurium from copper-bearing and lead-bearing metals, ores, or other specimens have rendered such prior methods slow and relatively costly to operate in commercial laboratory practice.

Moreover, another difliculty which has been experienced inthe electrolytic quantitative determination of copper and lead has been the fact that the oxygen and N02 which accumulate upon the anode during the electrolysis tend to adhere firmly to the anode where they retard deposition,

cause spongy deposits of PbOz, and otherwise generally cause inaccurate quantitative results,

electrolysis to form ferric nitrate which is an a excellent solvent for copper, and tends to dissolve the metallic copper deposited upon the cathode and thus cause inaccurate quantitative determi nations of copper. theferric nitrate has made it especially difficult to release all of the Cu ions from the electrolyte and to deposit the same upon the cathode. This solvent action of HNOs upon copper is particularly noticeable in the presenceof HNO2 in the electrolyte.

However, in the practice of the present invention it is possible to make accurate quantitative determinations of copper in copper-bearing metals and ores which contain as much as 1.5 or even 2.0 per cent iron.

Another difficulty which has been experienced in the use of prior methods and apparatus for the quantitative electrolytic determination of copper and lead is the fact that oxidizing gases, such as N02 and 02, formed in the electrolyte during the. electrolysis, tend to migrate to and to adhere firmly to the anode whereas, on the other hand, reducin gases such as H2 and NH3 tend, of course, to migrate to but do not tend However, the adherence of such oxidizing gases as N02 and 02 upon the anode tends to build up the internal resistance of the electrolyte, thereby causing excessive overvoltage with resulting formation of spongy and irregular and loosely adhering deposits of metallic copper and P1002 upon the cathode and anode, respectively.

The foregoing and other problems which are involved in the quantitative electrolytic determination of copper and lead have been recognized heretofore in the art and attempts have been made in various ways to overcome these difliculties. Thus, for example, mechanical electrolyte Thus the solvent action of stirring devices, rotating electrodes, and other mechanical devices have been employed and air stirring of the anode by the introduction of air into the electrolyte have all been employed. However, none of these prior mechanical devices or methods has, insofar as I am aware, been entirely successful, for a number of reasons. Thus one of the serious difficulties involved in the use of mechanical electrolyte stirring devices is the fact that such mechanical electrolyte stirring devices tend to dislodge the deposits of copper and PbOz from the cathode and anode, respectively, whereas agitation or scouring of the anode with air,

while tending to dislodge the firmly adhering oxidizing gases such as N02 and 02 from the anode, has no chemical eilect in preserving the pH of the electrolyte within desired limits or in preventing imbalance and resulting overvoltage of the electrolyte with consequent formation of spongy and irregular-shaped and loosely adhering deposits of copper and PbOz upon the cathode and anode, respectively. Moreover, the use of rotating electrodes, not only tends to dislodge the deposit accumulated thereon but renders it difficult to maintain the characteristics of the current and of the electrolyte employed constant durin the electrolysis.

Accordingly, an object of the present invention is to provide a new and. improved method for the quantitative electrolytic determination of copper and lead in copper-bearin and leadbearing metals and ores and which, in use, overcome the foregoing and other difficulties experienced in the use of prior methods and apparatus for the quantitative electrolytic determination of copper and lead.

An additional object of the present invention is to provide a new and improved method for the quantitative electrolytic determination of copper and lead and in the use of which more exact and more rapid quantitative electrolytic determinations of these metals can be made than has been possible heretofore in the use of prior methods and apparatus.

A further object of the invention is to provide a new and improved method for the quantitative electrolytic determination of copper and lead and in the use of which deposition-retarding and oxidizing gases, such as N02 and 02, which tend to gather upon and to adhere to the anode, and to cause spongy and loosely held deposits thereon, are continuously and thoroughly removed from the anode during the electrolysis without dislodging therefrom the PbOa deposited thereon.

A further object of the invention is to provide a new and improved method for the electrolytic determination of copper and which in use make it possible to obtain accurate quantitative determinations of copper in specimens containing as much as 2.0 per cent of iron.

Still another object of the invention is to provide a new and improved method for the quantitative electrolytic determination of copper and in the use of which the internal resistance of the electrolyte due to oxidation of the HNOS to NH; is min mized and the pH of the electrolyte is maintained within the range of from 5.0 to 5.5, and the current density is, therefore, kept substantially constant, thereby assuring good firm deposits of metallic copper upon the cathode and good firm deposits of P1002 upon the anode.

Another object of the present invention is to provide a new and improved method for effecting the relatively rapid and yet highly accurate quantitative determination of copper and lead in copper-bearing and lead-bearing metals, ores, or like specimens, in acid solution, and without the necessity for the prior separation from such specimens of such quantities of arsenic, iron, sulphur, phosphorus, molybdenum, selenium and tellurium, as may be present therein.

In the drawing:

Fig. 1 is a side elevational View, partly in section, illustrating a preferred form of electrolysis apparatus which may be employed in the practice of the present invention;

Fig. 2 is a Vertical sectional view illustrating the construction of the anode and related parts of the electrolysis apparatus shown in Fig. 1;

Fig. 3 is a bottom plan view, on line 33 in Fig. 2, illustrating the construction of the anode apparatus shown in Fig. 2;

Fig. 4 is a top plan view, on line 4-4 in Fig. 2, of the anode apparatus shown in Fig. 2; and

Fig. 5 is a partial sectional plan view on line 5-5 in Fig. 1.

A preferred form of the electrolytic apparatus which may be employed in the practice of the present invention is illustrated in the drawing, wherein it is generally indicated at it), and comprises an anode unit, which is generally indicated at H, and a cathode unit which is generally indicated at 12, both of which are shown as being arranged in an electrolytic beaker 13. The anode unit H includes a tubular metal combination current-conducting and gas-conducting member I4 to which a lead-in conductor 15 may be attached for connection to a suitable current source. The anode unit H also includes a preferably sandblasted and substantially cylindrical platinum wire gauze electrode is of suitable mesh. The combination current-conducting and gas-conducting tubular member I4 extends through a central opening I8 which is provided in a spider member I! which is attached in any suitable manner, as by a friction fit, upon the open upper end portion of the platinum wire gauze anode elect-rode 16 (Figs. 2 and 4). The lower end portion I9 of the combination current-conducting and gas-conducting tubular member I4 extends downwardly below the open lower end of the platinum wire gauze anode electrode it where the said lower end portion 39 of the said tubular member M is socured, in any suitable manner, as by welding, in a central opening 20 which is formed in a substantially circular closure member or cap 21 having an upper flanged portion 22 which is at tached in any suitable manner, as by welding, to the outer surface of the lower end portion of the substantially cylindrical platinum wire gauze anode electrode l6 (Figs. 2 and 3). As shown in Figs. 2 and 3, the lower end portion I9 of the tubular member 14 has an open lower end 24 which opens onto and below the lower surface 25 of the closure member or cap 2| and which is curved convexly downwardly, as best shown in Fig. 2.

The anode unit ll is completed by a flexible rubber tubular member 28 which is attached to the open upper end portion of the combination current-conductin and gas-conductin tubular member Hi so that the said tubular member M28 may be connected to a suitable source of carbon dioxide under pressure of from 1 to 15 pounds per square inch.

The usual procedure followed in the practice 5, of the present invention is illustrated in the following example:

EXAMPLE 1 In the practice of the present invention, a 1 gram sample of a copper-containing and leadcontaining metal may be dissolved in from 7 to temperature near boiling, on a hot plate, for a period of at least 30 minutes. During this phase of the operation the tin and antimon contents of the specimen, if any, will be precipitated as SD02 and SbzOs and these oxides, as precipitated, will carry down with them, out of the solution, a part of the iron content, if any of the specimen, together with most of the phosphorus content thereof. Since SnOz and SbzOs are soluble at temperatures below 65 C., but are insoluble at temperatures in excess of 65 0., the thus precipitated SnOz and Sb203 are filtered from the solution while the latter is kept hot. The filtrate solution is then ready to be electroanalyzed for its copper and lead contents.

The procedure thus described is the general procedure followed in preparing most specimens of copper-bearing and lead-bearing metals and ores for electroanalysis according to the method of the present invention and is varied only in those instances in which the sample or specimen is an aluminum bronze or a manganese bronze in either of which cases a one gram sample or specimen is dissolved in a hydrofluoric acid-resistant beaker with 7 c. c. of concentrated HNOs and from 3 c. c. to c. c. of hydrofluoric acid. This procedure keeps all of the tin and antimony in suspension so that the electroanalysis or quantitative determination of the copper and lead contents of the specimen may be accomplished without the prior removal of the tin and antimony contents of the aluminun bronze or manganese bronze specimen.

The electrolyte thus prepared is then transferred to the beaker l3 (Fig. 1) and the anode unit it and the cathode unit l2 are immersed therein whereupon the control valve (not shown) for the CO2 supply to the combination currentconducting and gas-conducting member l4-E8 is adjusted to produce a steady flow of CO2 at a selected pressure of from 1 to 5 pounds per square inch through the tubular member I l-28, whereupon the current from the lead-in conductors l5 and 2'! to the anode and cathode units H and i2, respectively, is turned on. The electrolysis thereupon proceeds in the electrolysis beaker E3, the copper content of the electrolyte being deposited as metallic copper upon the substantially cylindrical platinum gauze cathode 29 and the lead content of the electrolyte being deposited as P1002 upon the substantially cylindrical platinum gauze anode l6.

It has been found, in the practice of the present invention, that when the acid content of the electrolyte is relatively high all of the lead content of the electrolyte is deposited as F002 upon the anode I6 within a period of from 10 to 12 minutes from the time the electrolysis is begun depending, in part, upon the current density, voltage, and other variables.

In order to produce a sharper separation of the copper content of the electrolyte, and a better grained and more firmly adhering deposit of metallic copper upon the cathode 29, 2 c. c. of concentrated H2804 are at this stage of the electrolysis added to the electrolyte in the beaker l3 and the electrolysis continued until a spot test of one drop of the electrolyte with I-IzS water shows that all of the lead content and all of the copper content of the electrolyte have been deposited upon the anode l6 and upon the cathode 29, respectively.

The current to the lead-in conductors l5 and 2t and the flow of CO2 through the tubular member l428 may then be shut off and the anode and cathode units H and [2, respectively, removed from the beaker I3. The anode unit H may then be dried in an electric oven for a period of about minutes, at a temperature of about 200 C., and then weighed with the thus dried deposit of PbOz thereon. The cathode unit I2 and the deposit of metallic copper thereon may then be dipped in boiling water and alcohol and then dried for a period of 2 minutes at a temperature of 110 C. Upon subtracting from these weights the net known weights of the anode and cathode units H and 12, respectively, the weight g of the metallic copper deposited upon the cathode 29 and the weight of H302 deposited upon the anode It may be determined and the copper and lead contents of the specimen or sample thus analyzed readily calculated.

It has been found in the practice of the present invention that as the CO2 flows downwardly through the combination tubular current-conducting and gas-conducting anode member M it emerges in the form of a steady stream of CO2 bubbles from the open lower end 24 of the tubular member M whence the CO2 bubbles pass upwardly over the convexly downwardly curved bottom surface 25 of the closure member or cap 2| which is attached to the lower end portion of the substantially cylindrical platinum gauze anode member E6.

Moreover, it has also been found in the practice of the present invention that as the CO2 bubbles emerge from the open lower end portion 24 of the tubular member i4 and travel upwardly in the electrolyte over the convexly downwardly curved lower surface 25 of the member 2| the said convexly downwardly curved lower surface 25 of the memberZl imparts a whirling motion to the CO2 bubbles and as the stream of whirling CO2 bubbles pass upwardly in the electrolyte over the external surface of the substantially cylindrical platinum gauze anode is the said CO2 bubbles create a turbulence and exert a scouring action upon the said platinum gauze anode l6 and upon the deposit of PbOz thereon and which results are not obtained when the bottom of the closure member 2! is formed as a square or other substantially fiat surface. In this manner substantially all of the deposition-retarding and oxidizing gases, including 02 and N02. which accumulate upon the platinum gauze anode l6 and upon the PbOz deposit thereon (and which deposition-retarding and oxidizing gases would otherwise cause spongy and loosely held deposits of P1002 as well as building up the internal resistance of the electrolytic cell), are removed from the platinum gauze anode It and the P1002 dee posit thereonin status nascendi. In this manner good uniform andl firmly held deposits of PbOz on the anode Eli are assured, the internal resistance of the electrolytic cell is minimized and overvoltage in the electrolytic cell is elimi-i nated, oxidation and resulting staining of the copper deposited on the cathode 20 are prevented and good firm deposits of salmon-colored copper on the cathode 29 are obtained, the tendency of the ferric nitrate content in the electrolyte to increase with resultant corresponding increase in the solvent action of the ferric nitrate upon the copper deposited on the cathode 29 is counteracted and reduced, and more accurate quantitative electrolytic determinations of both lead and copper are assured.

It has also been found in the practice of the present invention that the steadily flowing stream of CO2 bubbles thus passed into the electrolyte not only exerts a mechanical scouring or cleaning function upon the platinum anode IE and upon the PbO2 deposit thereon, so as to remove in status nascendi the deposition-retarding and oxidizing gases, such as 02 and N02, which would otherwise adhere and cling to the anode l6 and the PbOz deposit thereon, but the steady flow of CO2 thus passed into the electrolyte during the electrolysis performs a second but not fully understood function which is believed to reside in the formation of carbonic acid (HzCOs) in the electrolyte and which tends to neutralize the NH3 which is formed in the electrolyte, particularly in the latter stages of the electrolysis. Hence it is believed that the CO2 thus functions to maintain a definite acidity in the electrolyte throughout the electrolysis and thus keeps the temperature of the electrolyte down, preserves a more uniform current flow through the electrolyte, and thus accelerates and promotes the deposition of the last traces of copper and lead in the electrolyte upon the cathode and anode, respectively, with correspondingly more accurate quantitative electrolytic determinations of these metals than has been possible heretofore in the use of prior methods and apparatus. That such a second function is performedby the CO2, in addition to its function of mechanically scouring the platinum anode l and the PbOz deposit thereon, is shown by the fact that if a stream or" air is passed through the tubular anode member i i-28, in place of a stream of (202, but under otherwise identical conditions, and with all other variables controlled, the results in terms of quantitative electrolytic determinations of copper and lead are significantly and consistently less accurate than when a stream of CO2 is employed, as in the practice of the present invention. That this is so may be seen by reference to the following comparative examples.

Thus a typical analysis of a sample of brass, of known composition, to determine its lead and copper contents, following the practice of the present invention, is illustrated in the following example:

EXAMPLE 2 The cathode 29 was formed of a sandblasted 45 mesh platinum gauze cylinder which was 35 mm. in diameter and 50 mm. in heighth. The anode It was formed of a sandblasted 45 mesh platinum cylinder which was 15 mm. in diameter and 50 mm. in heighth. After an initial polarizing period of one minute the current in the electrolytic cell was adjusted by means of a rheostat to two amperes at an average potential of 2.2 volts and the current was held constant at this density and voltage throughout the analysis. A certified National Bureau of standards sample of brass weighing 1.000 gram, plus or minus 0.1 milligram, and having the certified composition hereinafter set forth, was then dissolved in 10 cc. of concentrated HNOs, baked to dryness, redissolved in 70 cc. of concentrated HNOa, digested with 30 cc. of boiling water for 20 minutes, and then filtered through a No. 42 Whatrnan filter paper at a temperature slightly in excess of 70 C. The filtrate was then cooled to room temperature, diluted to approximately -110 cc., and placed in the beaker l3. The electric current was then adjusted and the CO2 gas was then passed through the tube '14 as set forth above. After twenty minutes of elapsed electrolysis time 40 cc. of 1-1 H2SO4 were added to the electrolyte in the beaker 13. After disappearance of the blue color in the electrolyte, a small quantity of hydrazine sulphate was then added to the electrolyte to accelerate the deposition of the last traces of Cu ions. Completion of the electrolysis was ascertained by repeated additions of a drop of the electrolyte to a small specimen or pool of H28 saturated water on a porcelain spot-plate until no yellow discoloration took place. Upon completion of the electrolysis the parts of the anode unit II and the parts of the cathode unit l2 were dipped in a solution of boiling water and methyl alcohol and then dried in an electric oven before weighing. Thus the parts of the cathode unit '12 were dried for a period of from 2 to 3 minutes at a temperature of C. and the parts of the anode unit H and the deposit of 'PbOz thereon were dried for a period of 45 minutes at a temperature of 200 C., whereupon the thus dried parts of the cathode unit i2 and the thus dried parts of the anode unit ii and the deposit of PbOz thereon were then weighed and the weight of the Cu and PbO2 deposit on the anode unit Ii determined.

Four samples of the same certified specimen of brass were analyzed in the manner set forth above and the accuracy of the analyses made may be seen by comparing the results obtained with the certified known composition of these brass specimens as furnished by the United States Bureau of Standards, as follows:

Certified composition of sample Percentage by weight Copper 83.77 Lead 4.78

Zinc 5.46

Tin 1- 4.69

Nickel 0.45

Tin 0.38

Antimony 0.23 Silicon 0.075

Sulphur 0.071

Phosphorus e l l 0.037 Aluminum l 0.016

Copper and lead contents of brass sample as obtained by the method of Example 2 Electrolysis Specimen Number Element Time in Percentage Minutes by Weight 1 1. Copper Lead" 43 2 o 43 1% 3 do---. 48 i: 4 d0 4s 2 9 EXAMPLE 3 In order to illustrate the greatly reduced deposition time and resulting increased speed of electrolysis and the markedly higher degree of accuracy in the results obtained a specimen of the same United States Bureau of Standards sample of brass referred to above, and having the certified composition set forth above, was analyzed exactly in accordance with the method and the conditions set forth in the foregoing Example 2 except that the CO2 flow through the anode tube It was shut off and the electrolysis made without passing CO2 into, or otherwise agitating, the electrolyte. The results obtained were as follows:

Electrolysi' Percentage Specimen Number Element Time by Weight Hours 1 Copper Lead g:

EXAMPLE 4 In order to illustrate the greatly reduced deposition time and the much greater accuracy in the quantitative determinations of lead and cop per obtained when directing a steady stream of CO2 through the tubular anode member I l-28', as compared with the results obtained when air, rather than CO2 was directed into the electrolyte through the tubular anode member 14-28, analyses of the same certified Bureau of Standards brass sample were run exactly in accordance with the method and conditions set forth in the foregoing Example 2 except that air, rather than CO2 was allowed to flow through the tubular anode member l4-28 under exactly the same pressure and conditions as were employed Similarly, a certified Bureau of Standards sample of phosphor bronze was analyzed exactly in accordance with the method and under the conditions set forth in the foregoing Example 2, with the following results:

Certified composition of sample Percentage by v weight Copper 78.50 Lead 8.92 Tin 9.79 Zinc 0.61 Phosphorus 0.59 Iron 0.52 Antimony 0.50 Nickel 0.32

Sulphur 0.11 Arsenic 0.026

Copper and lead contents of sample of phosphor bronze as determined by the method of Example 2 Electrolysis P Specimen Number Element Time in 2 Minutes by Wel=ht Copper I 45 1 l 2 ii 2 p 4 3 45 3.89 opocr .46 4 {Lead 45 8.93

EXAMPLE 6 In order further to illustrate the greatly reduced deposition time and the greater accuracy in the quantitative determination of lead and copper which are obtained when passing a stream of CO2 through the tubular anode member 14-28 into the electrolyte, specimens of the sameBureau of Standards sample of phosphor bronze, having the certified composition set forth above, were analyzed exactly in accordance with the method, and under the conditions set forth in Example 2, above, except that the flow of CO2 through the tubular anode member l4-28 was shut off and the electrolysis was made without agitating the electrolyte in any way. The results were as follows:

Specimen Number Element g gg s15 Hours EXAMPLE '1 In order further to illustrate the greatly reduced deposition time and the much greater accuracy obtained when directing a stream of CO2 through the tubular anode member l4--28 into the electrolyte, as compared with the results obtained when employing air in place of CO2, analyses of the same certified Bureau of Standards sample of phosphor bronze were made exactly in accordance with the method, and under the in the use of CO2.

conditions, set forth in Example 2, except that a stream of air, rather than CO2, was directed through the tubular anode member l4-28, under exactly the same conditions as were employed The results were as follows:

Specimen umber Element g ig g 1 d }1 ou 57 7g 2g #2 v d 57 7g: 3 {L d hour 30 4 {L d }1 h0l1I, 30 1 86 In place of the nitric acid-sulphuric acid electrolyte which was employed in the analyses of the specimens of brass in Examples 1 to 4, inclusive, and in the analyses of the specimens of phosphor bronze, as in Examples 5, 6 and '7, an electrolyte consisting of a mixture of nitric acid and hydrofluoric acids may be employed in the practice of the present invention as when analyz- Aluminum -l 0.001 ing a specimen of aluminum bronze or manganese bronze to.- determi-nethe copperand lead. contents thereof. Thus a specimenof manganese bronze was analyzed: in. the; apparatus illustrated in the drawing, according to the procedufe illustrated in the. following example:

EXAMPLE 8 A specimen of manganese bronze weighing 1.000 gram was placed ina 200 c. c. hydrofluoric acid resistant beaker. The following materials were then added to the beaker in the order named: c. c. H; 1 c. c. 48 per cent water solution of hydrofluoric acid; and 7 c. c. concentrated HNOs. The beaker was then covered with a platinum lid, and the electrolyte allowed to stand, without heating, until the sample was entirely dissolved, whereupon the solution was boiled briefly to drive off excess N02. The solution was then. cooled to room temperature, the lid and beaker rinsed, with water, the solution diluted with H2O: to 2.00- c. and; the electrolyte then placed in the beaker I3 of the electrolysis. apparatus shown in the; drawing. The current density was then; adjusted to from 1.075 to 2 amperes, and the CO2 stream through the tubular anode member [4-28 turned on. The electrolysis was thereupon allowed to proceed and the entire lead content of the: specimen was. depositedas' PbOz, upon the anode, which was accomplished in 20minutes. 4 c. c'.,1-l H2504 were then added to the electrolyte and the analyses then completed in the manner set forth in Example 1.

The hydrofluoric acid content of the electro lyte employed in the foregoing Example 8 serves to keep the antimony and tin content of the specimen of manganese bronze in solution so that it will not contaminate either the copper or the lead dioxide (PbOz) deposit. during the analyses to determine the copper and lead contents of the specimen of manganese bronze.

The results obtained in the determination of the lead and copper contents of specimens of manganese bronze according to the method of the present invention are equally as accurate as the results obtained in determining the lead and copper contents of. samples of brass and phosphor bronze, and similar copper-bearing and, leadbearing, metals, as in Examples 1 to '1, inclusive, above.

Moreover, in the practice of the present invention it has been found possible to obtain accurate and rapid electroanalyses of copper in the presence of substantially greater percentages of bismuth andironthan has beenpossible heretofore, notwithstanding the strong solvent action of iron, in the form of ferric nitrate, upon copper deposited upon the cathode during the electroanalyses. Thus accurate and rapid quantitative determinations of copper have been obtained from brass samples, using HNO3H2SO4 as the electrolyte, in the presence of as much as 0.5 per cent iron in the sample, and in the analysis of specimens of bronze, using HNO-3HF as. the electrolyte, accurate quantitative determinations of copper have been obtained in the presence of as much as 3.0- per cent iron inthe sample.

It will thus be seen from the foregoing description, considered, in conjunction with the accompanying drawing, that the present invention. provides a new and improved. method for the rapid and accurate quantitative. electrolytic determination of lead andv copper in lead-bearing. and copper-bearing metals, ores, and the. like, and that the invention thus has the desirable advantages and characteristics, and accomplishes its:- intended objects, including those hereinbefore pointed out and others which are inherent in the invention.

I claim:

Ina method for the duantitatiye electrolytic determination of lead and copper indeed-copper materials, the improvement which resides in dissolving a, sample, of the material in nitric acid to form an electrolytic: solution, electrolyzing said solution. in the presence of a cathode and a cylindrical gauze. anode to cause the lead content of the solution to be deposited as PbOa on said anode and the copper content of the solution to be deposited on said cathode, passing a continuous stream of CO2 gas into the solution immediately below said anode during the electrolysis so that the said CO2 gas will travel upwardly through the solution and create a turbulence about the anode and thus. exert a scouring action upon, the anode and upon the PbOz deposited thereon to remove oxidizing gases such as 02 and N02 which tend to accumulate upon and adhere thereto, adding sulphuric acid to the solution after substantially all of the. lead content of the solution has been deposited as P1002 on, the anode to improve the. grain structure of the copper deposited upon the cathode and to cause the copper to adhere more. firmly thereto and continuing the electrolysis until substantially all the copper has been deposited on the cathode.

ROBERT W. NOTEST'.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 563,093 Szontagh et al. June 30,1896 1,254,045 King Jan. 22, 1918 2,370,871 Marks Mar. 6, 1945 OTHER REFERENCES Zeitschrift fur Elektrochemie, vol. 17 (1911), pp. 905, 906;.

Elektro-analytische Schnellmethoden by Fisher, 1926., pages 2&2 through 246'.

Journal of the. American Chemical Society, vol. 54, March 1932, pages. 8.7.7 to 881.

Handbook of Chemistry by N. A. Lange, 1934, pages 702, 703.

A. S. T. M. Methods of Chemical Analysis of Metals, 1943, published by American Society for Testing Materials, pages 12, 13, 170, 273. 

